The industry and tradesmen are under obligation, to avoid polluting the waste water whenever possible or, on the basis of §7a Section 1 Sentence 4 of the Federal Water Act, if the waste water contains hazardous substances, to clean up the waste water on the basis of the state of technology. In the Recycling Management and Waste Act, the avoidance of waste has the highest priority.
The increasing demands on industry and municipalities with regard to wastewater treatment plants do not only create greater volumes of wastewater to be treated and sewage sludge to be disposed off, but often also cause problems with regard to the characteristics of the sludge and make the competent disposal of the waste more difficult. For example, the separation of the sludge in many municipal wastewater treatment plants has significantly decreased since the phosphate elimination has been started.
Innovative processes for waste water and sludge treatment as well as the raising of the efficiency of mechanical treatment plants are thus gaining more and more in importance through the increase in the streams of waste in many areas of environment and process engineering. The difficulties arising in the exploitation/disposal of waste require always improving conditioning and treatment processes in order to reduce the amount of waste and even to recover materials.
Therefore, pre-treatment processes are necessary that enable the separation of the colloid components through filtration and sedimentation for economic and ecological reasons. Contaminates are often suspended in the wastewater and very finely emulated and distributed. In such systems the alignment of the negative charge of the particles in the same direction has a disadvantageous effect, which make the efficient separation in mechanical installations more difficult and necessitates the use of chemical additives, such as polymeric and/or organic flocculation agents.
The pre-treatment of these waste streams can alternatively be carried out using electro-physical precipitation. In that case the electrically charged particles are moved in the electrical field to the electrodes, neutralised there and thus the coagulation of the particles effected. Depending on the wastewater composition additional oxidation processes may result in the removal of certain water content substances during the application of the electro-chemical process. The knowledge of the mechanism of the various reactions is thus of particular importance for the optimisation of the process and for the adjustment to the special requirements in the case of the substance systems to be treated. Therefore the consideration of the electro-chemical theory, on which this is based, is of particular importance for the development of the process.
Some examples of prior art documents, which may relate to the background of the present invention, are briefly described herein for discussion purpose.
U.S. Pat. No. 6,55,977 briefly teaches in one aspect an electrolytic purification method and apparatus for treatment of wastewater to reduce chemical oxygen demand, by oxidation of water-soluble organic and other oxidizable materials contained therein. The electrolytic purification system of the invention utilizes one or more electrochemical cells. The cells employ stainless steel electrodes and contain iron chips, which are mobile and circulate freely as liquid flows through the cell. The iron chips are in electrical contact with the anode and are prevented from making contact with the cathode by a non-conductive but liquid-permeable barrier. The iron chips thus provide a dynamic and fluid electrode surface that is efficient and resistant to performance degradation.
This invention relates in another aspect to an electrolytic oxidation apparatus, comprising two or more electrochemical cells, arranged in series for sequential flow of wastewater there through to affect the desired level of COD removal. In one specific embodiment, the invention relates to an electrolytic oxidation process for purifying a wastewater stream by oxidation of water-soluble organic and oxidizable inorganic substances contained therein.
U.S. Pat. No. 6,325,916 briefly teaches a method for separating contaminants from a aqueous source containing contaminants. In one embodiment, the method involves the use of a high powdered oxidant dissolved within the aqueous system. The gas is dissolved within a reservoir in the aqueous solution and the pressure within the reservoir is controllable. This allows maximum contact of the oxidizing dissolved gas with the contaminant material. Once oxidized, the outlet of the reservoir is adapted to permit hydraulic cavitations. The net effect of the cavitations is to induce a foam formation which foam transports a floc into a separate phase from the aqueous solution. In this manner, the process is effectively a dissolved oxidizing gas mass transfer process. In another embodiment, the process may be augmented by electrocoagulation. This involves the use of an electric cell which is disposed within the reservoir containing the oxidant material. By providing electrodes and exposing the electrodes to a source of current, the contaminants within the aqueous solution are either oxidized or otherwise degraded and this complements the oxidation by the dissolved gaseous oxidant.
U.S. Pat. No. 6,740,245 briefly teaches an invention to provide extremely efficient, low maintenance, low energy cost modular water purification and contamination control technology for the non-chemical disinfection and contaminant separation of various types of water or wastewater streams. The water treatment and purification areas of particular interest include, but are not limited to, drinking water, ship ballast water, marine discharge wastewater, commercial and industrial cooling water, industrial and commercial hazardous and/or toxic effluents, manufacturing process water, industrial machine tool coolants, sewage, and agricultural and food processing streams.
Specifically, the non-chemical water purification and disinfection technology of the invention exhibits higher treatment efficiency than more conventional water treatment methods that rely on chemicals, traditional filtration, reverse osmosis, ozone generators, etc, and also involves reduced energy costs. By eliminating the treatment chemicals, increasing sub-micron particle size solids separation and removal, and by very efficient destruction of bacteria and biological agents within the treated water through electrically-driven disinfection; a number of operational, maintenance and serious health and water treatment problems can be eliminated, resulting in the economic recovery of contaminated water, and ultimately in conservation, purification, and protection of shrinking drinking water supplies. Accordingly, it is the object of the this invention to establish non-chemical water treatment disinfection and purification technologies that represent realistic, “user friendly”, and cost effective answers to global water availability issues and concerns.
U.S. Pat. No. 4,149,953 briefly teaches a treating chamber operable as an electrolytic cell is provided, in which the electrodes have large surface areas relative to the volume of the electrolyte. The anode is composed of a quantity of aluminum particles and the cathode is composed of a quantity of iron particles disposed in close proximity to the aluminum. Wastewater containing impurities is introduced into the treating chamber and utilized as the electrolyte. An electric current is applied to the electrodes to dissolve aluminum and iron, and produce floc in the treating chamber. The impurities in the water are adsorbed and retained by the floc. The wastewater may be continuously re-circulated from the treating chamber to a holding chamber, or may be moved across the aluminum and iron electrodes in a continuous flow-through system at a predetermined flow rate. The floc containing the adsorbed impurities is separated from the water by conventional means. As an alternative, clean water containing normal dissolved solids may be introduced into the treatment chamber and utilized as the electrolyte. An electric current is applied to the aluminum and iron electrodes to produce floc. Floc-laden clean water is conveyed to a chamber containing wastewater, and mixed therewith. Floc containing impurities adsorbed from the wastewater then is separated from the water by conventional means.
U.S. Pat. No. 6,793,801 briefly teaches a method and apparatus for contaminant separation utilizes an interleaved array of oppositely charged electrode plates for fluid treatment. Spacing between the parallel electrode plates is graduated so that the volume of the cavities between the opposing electrodes provides varying levels of treatment of a broad range of contaminants from a variety of fluid columns. A fluid flow path extending substantially orthogonal to the direction of the electrical field established between opposing electrode plates provides a feed stream with exposure to the varying levels of electrical charges between the electrode plates. The method and apparatus provides an effective means of contaminant separation by a device having a small footprint and requiring low amounts of electrical energy.
U.S. Pat. No. 6,923,901 briefly teaches an invention to provide extremely efficient, low maintenance, low energy cost modular water purification and contamination control technology for the non-chemical disinfection and contaminant separation of various types of water or wastewater streams as encountered in the marine industry. The water treatment and purification areas of particular interest include, but are not limited to, ship ballast water and marine discharge wastewater. Specifically, the non-chemical water purification and disinfection technology of the invention exhibits higher treatment efficiency than more conventional water treatment methods that rely on chemicals, traditional filtration, reverse osmosis, ozone generators, etc, and also involves reduced energy costs. By eliminating the treatment chemicals, increasing sub-micron particle size solids separation and removal, and by very efficient destruction of bacteria and biological agents within the treated water through electrically-driven disinfection, a number of operational, maintenance and serious health and water treatment problems can be eliminated, resulting in the economic disinfection of ballast water and the like and thus avoiding spread of nonindigenous species. Accordingly, it is the object of the this invention to establish non-chemical water treatment disinfection and purification technologies that represent realistic, “user friendly”, and cost effective answers to global water issues and concerns, particularly in the marine and maritime-related industries.
U.S. Pat. No. 6,613,201 briefly teaches an apparatus for treating water by means of an electric field. An Anode and a cathode are arranged in a treatment chamber. The cathode has a plurality of parallel pins. Seed crystals are deposited on these pins. There are means for separating these seed crystals from the pins. The apparatus is to be of simple design and is to have high efficiency with regard to the formation of seed crystals. The cathode is to be kept free from lime depositions. To this end, the seed crystals are separated or stripped from the pins by means of a perforated disc. The pins extend through the holes of this perforated disc. The perforated disc is guided over the pins. The perforated disc can be moved by water pressure or by an electric motor. The electric motor has as second function the actuation of a safety valve controlled by a monitoring device.
U.S. Pat. No. 6,849,178 briefly teaches an apparatus for water treatment by means of an electrical field is provided with an anode and a cathode in at least one treatment chamber through which the water to be treated passes. The apparatus is characterized in that the at least one treatment chamber forms a prismatic space with an elongated cross section, the anode and the cathode are formed by pairs of parallel, stick-shaped electrodes which extend spaced apart into said space and a voltage is applicable between the electrodes. One end of the at least one treatment chamber is connected to a water inlet and the other end of the at least one treatment chamber is connected to a water outlet, whereby a waterflow from one electrode to the other is generatable which is substantially transverse to the longitudinal axes of the electrodes.
U.S. Pat. No. 6,122,599 briefly teaches an apparatus for analyzing particles suspended in a fluid. The fluid has electrical properties different from that of the particles. The fluid and particles move from a first fluid containing portion to a second fluid containing portion through a conduit or aperture. A first pair of electrodes, each electrode of the pair being in a respective fluid containing portion. A constricted electrical path is defined between the first and second electrodes, and the path extends along the aperture. At least one other pair of electrodes is positioned in a non-encircling arrangement, and is aligned with each other and transverse to the constricted electrical path. This configuration eliminates many common errors susceptible to other devices.
U.S. Pat. No. 6,338,789 briefly teaches an apparatus for treating water by means of an electric field. An anode and a cathode are arranged in a treatment chamber. Seed crystals are deposited on the anode and are stripped there-from to be carried along with the water, which cause crystallization thereon of carbonates contained in the water. Thereby formation of boiler scale, when the water is heated, is reduced. The water from the treatment chamber is exposed to another electric field in an after-treatment chamber for a dwell time longer than the dwell time in the treatment chamber. Thereby, the growth of the seed crystals is enhanced. The efficiency of a treatment chamber with after-treatment is higher than the efficiency of the treatment chamber alone.
U.S. Pat. No. 4,104,142 briefly teaches a liquid containing suspended solids is first passed through an electrostatic treater, having no current flow across its electrodes, to initiate nucleation and coagulation of the particles. Thereafter, it passes through an electrolytic treater wherein current may flow between the electrodes to further encourage coagulation to such an extent that flocculation begins. The residual effects of the electrostatic treater prevent plating out on the electrodes of the electrolytic treater such that electrolysis can occur without sacrificing an electrode, and the electrodes are so arranged that the liquid passes sequentially through groups of concentrated lines of force whose repetitious, powerful action further encourages flocculation. From the electrolytic treater, the liquid with its flocculated material is delivered into a clarifying basin so designed that the floc will settle out and be removed from the basin with a minimum of manipulation because of the tendency of such material to immediately dissipate and disperse when handled while still in the liquid.
U.S. Pat. No. 3,944,478 briefly teaches an electrolytic drainage treating apparatus is provided to treat a drainage containing a suspension of contaminated compound whereby the suspension is flocculated and removed by aluminum ions or iron ions eluted by electrolysis. The electrolytic drainage treating apparatus is equipped with a high-speed electrolyzer comprising an anode and a cathode having a thin gap there-between through in which a drainage is forcibly passed as an electrolytic solution. The anode material such as aluminum and iron is eluted as ions by the electrolysis caused by passing electric current across the gap. The width of the gap between the anode and the cathode is controlled. The high-speed electrolyzer is effectively used for various electrolytic treatments.
U.S. Pat. No. 6,689,271 briefly teaches an electrocoagulation system for removing contaminants from waste effluents comprising an electrocoagulation reactor having charged and uncharged plates and allowing serial flow of water there-through. The reactor is connected to a voltage source to charge some of the plates positive and some negative, with uncharged plates between the positive and negative plates. The system allows wastewater to enter the reactor for coagulation therein, the waste water leaving the reactor to enter a defoam tank for agitation which allows trapped bubbles to rise to the surface of the tank as foam. From the defoam tank, waste water goes through a sludge thickener, to allow sludge to settle at the bottom thereof and waste water is drawn off from the sludge thickener to flow to a clarifier. The pump removes sludge forming at the bottom of clarifier to take it back to the sludge thickener. The sludge is drawn-out the bottom of the sludge thickener for transport to a press where most of the water is removed there-from. Water is drawn off the top of the clarifier for transport to a conventional sewer system, or for reuse.
U.S. Pat. No. 6,315,887 briefly teaches a device for the purification of polluted water, especially adapted to remove there-from organic pollutants. The device makes use of a reactor wherein the polluted water is subjected to the combined action of an ozone containing gas in the presence of an oxidation reaction catalyst that is produced in-situ by electrolysis. An object of the invention to provide an efficient and economic method for the purification of polluted water, especially waste water, by either oxidation “in-situ” of its organic contaminants and/or combination thereof in a physically removal form. This method also permits to kill contaminating living pollutants such bacteria and virus. It is another object of the invention to provide a device for carrying out the aforesaid method. This device can be used for the purification of polluted water contaminated with a large variety of pollutants such as those found in the effluent of many organic processing plants. Thus, it becomes possible to achieve the treatment of water polluted with organic compounds, especially organic compounds found in the effluent of many polluting industries like petrochemicals, fertilizers, insecticides, pesticides, or in paper mills and food industries, which generally contain high COD and BOD level. It is a further object of the invention to provide a reactor in which high oxidizing conditions are generated so as to fully or partially break down organic pollutants and transform them into easily removable oxidation products, especially oxidation products having a low density or gas. Thus; this invention provides a method and a device, which permit to purify heavily polluted water. The method and device according to this invention are devised to oxidize the organic contaminants contained in the wastewater that is treated and to produce during the treatment at least one catalyst of oxidation reaction in a very activated state.
U.S. Pat. No. 6,294,061 briefly teaches an electrocoagulation system for removing contaminants from waste effluents comprising an electrocoagulation reactor having charged and uncharged plates and allowing serial flow of water there-through. The reactor is connected to a voltage source to charge some of the pates positive and negative plates. The system allows wastewater to enter the reactor for coagulation therein, the waster water leaving the reactor to enter a defoam tank for agitation which allows trapped bubbles to rise to the surface of the tank as foam. From the defoam tank, waste water goes through a sludge thickener, to allow sludge to settle at the bottom thereof and wastewater is drawn off from the sludge thickener to flow to a clarifier. The pump removes sludge forming at the bottom of clarifier to take it back to the sludge thickener. The sludge is drawn out the bottom of the sludge thickener for transport to a press where most of the water is removed there-from. Water is drawn off the top of the clarifier for transport to a conventional sewer system, or for reuse.
U.S. Pat. No. 6,274,028 briefly teaches a method and apparatus for purifying aqueous effluent streams to reduce chemical oxygen demand thereof, where the method comprises direct oxidation of water-soluble organic material in an electrochemical cell that incorporates stainless steel electrodes, whose stability and lifetime are enhanced by inclusion of circulating metal chips.
U.S. Pat. No. 6,126,838 briefly teaches a method for treating highly concentrated wastewater by electrolysis and oxidization, said method being characterized in that the electrolysis and oxidization are carried out in a fluidized bed of a suitable particulate carrier. The electrolytic reduction efficiency of ferric ions is improved by the fluidized particulate carrier; and thus a high proportion of iron (III) to iron (II) can be sustained in the system. This invention allows extensive purification of wastewater with improved efficiency.
U.S. Pat. No. 5,928,493 briefly teaches a process for the treatment of industrial waste water using electrocoagulation to effect separation of contaminants, which may include heavy metals, dyes, oils, fats, solvents, and salts. The process comprises passing waste water containing contaminants susceptible to electrocoagulation between pairs of electrodes within a reactor cell, energizing the electrodes with direct current, thereby breaking down and chemically altering contaminants in the electrolyzed water to form a sedimentable flocculate therein; and separating the flocculate from cleaned water. This invention also anticipates an apparatus for treating waste water which comprises: an electrocoagulation reactor cell having spaced-apart electrodes energized by direct current, a pump for passing industrial waste water through the reactor and between the electrodes, a de-foam tank, a mechanical clarifier, and a recessed-plate filter press.
U.S. Pat. No. 4,770,755 briefly teaches an electrode unit to be used for purification of emulsions and polluted waters, especially oil-bearing waters, by electrolysis which comprises vertically placed adjacent electrode plates of a soluble material, spacers for adjusting the distance between the electrode plates and equipment for adjusting the depth of immersion of the electrode plates. The tips of the electrode plates defines the only area of the plates in contact with the liquid to be purified and the depth of immersion of the electrode plates is adjusted in order to keep the current density between the electrode tips within a desired area. In addition, the space in between the plates is also adjusted in order to keep the current density between the electrode tips within the desired area.
U.S. Pat. No. 4,623,436 briefly teaches a method and apparatus for removing impurities from a liquid, the liquid containing impurities is supplied to an electrolytic bath at a pressure higher than atmospheric pressure. Electrolysis is performed by applying a voltage to electrodes consisting of a metal, which easily dissolves upon electrolysis. The liquid is then exposed to atmospheric pressure, and is treated in a flotation separation tank. Fine bubbles formed during the treatment of the liquid in the flotation separation tank attach to the impurities flocculated in the liquid by electrolysis. The flotation separation of the flocculated impurities is performed very efficiently, and high-purity water can be recovered. The apparatus comprises an electrolytic bath consisting of a pressure vessel, in which electrodes of a metal which easily dissolves upon electrolysis are housed, and a constant current source for applying a voltage to said electrodes so as to obtain a predetermined current density in a liquid contained in said electrolytic bath, wherein impurities in the liquid are caused to flocculate by a hydroxide of the metal.
U.S. Pat. No. 4,181,591 briefly teaches a fluid, such as air or water, carrying suspended solids is directed between a pair of oppositely charged, corrugated surfaces in order to subject the flow to an undulating action that increases the frequency with which the solid particles impinge against one another, thereby increasing the rate of flocculation of the solids. In the case of airborne particles, the corrugated surfaces are arranged in an upright condition so that the flocculated particles attracted to one or the other of such surfaces gravitate there-from into a conveying mechanism that delivers such particles to a collecting receptacle. In the case of liquid-borne particles, the flow is forced to travel upwardly against the force of gravity after passing between the surfaces, thereby encouraging the flocculated particles to settle out into a sump that is associated with the uphill flow passage. In each case, two sets of charged surfaces may be utilized, the first having at least one of its surfaces insulated from the flow for electrostatic action only, while the second has neither surfaces so insulated for electrolytic action.
Additional to the above-mentioned prior arts, there are also several other prior art which basically relates to the background of the present invention such as DE 69021388 T2, DE 10046959 A1, DE 4330518 A1, 5474748 A and EP 0701972 A1.
Any discussion of documents, devices, acts or knowledge in this specification is included to explain the context of the invention. It should not be taken as an admission that any of the material forms a part of the prior art base or the common general knowledge in the relevant art in Singapore or elsewhere on or before the priority date of the disclosure and claims herein. All statements as to the date or representation as to the contents of these documents is based on the information available to the applicant and does not constitute any admission as to the correctness of the dates or contents of these documents.
In the electro-physical precipitation the present inventor(s) have found a separation process, which is clean, cost effective, comfortable and quick. Until now stable emulsions and suspensions required complex pre-treatment, before the individual phases could be treated. For example, emulsions such as drilling or cutting oil or wastewater from washing processes are often broken down through the addition of chemicals such as metal salt or polymers. The disadvantage of this procedure lies in the fact that metal salts cause salt accumulation. Another process is the emulsion separation through ultra-filtration. This process delivers an almost oil-free filtrate, which can be fed into the biological treatment. However, its acquisition as well as operation is relatively expensive. The same applies to thermal and thus energy-intensive separation processes. In contrast to the traditional routes, the electro-physical precipitation takes the direct path that covers the environmentally friendly cleaning of problematic wastewater or pre-treatment of water or wastewater for subsequent desalination.
Therefore, it is an objective of the present invention to introduce a so-called sacrificial anode, which will be slowly dissolved by sending metal ions into a liquid medium on the way to the cathode.
It is yet another objective of the present invention to generate highly reactive radicals as well as hydrogen and oxygen at the surface of the electrode. In particular, the radicals entail numerous secondary reactions with content materials of wastewater, as for example the degradation of organic substances through oxidation. This also reduces the chemical need for oxygen.
It is yet another objective of the present invention to generate the many-facetted areas of application of the electro-physical precipitation such as splits drilling and cutting oil emulsions as well as chalk and plaster suspensions. It eliminates heavy metals from galvanic wastewater. It can also be advantageously be used for pre-treatment of water or wastewater in desalination process.
Some advantages of the present invention are that the required space is small and the equipment expenditures low. No hazardous materials in the form of chemicals have to be stored and the operating costs are limited. The distance between the electrodes has been optimized with regard to a large surface per reactor volume. The voltage is comparatively low, which has a beneficial effect on the energy consumption. The wear and tear of the iron-aluminum or alloy-coated electrodes that serve as sacrificial anodes is also kept within modest limits.